Backpack



FIG. 1 is a front perspective view of a backpack showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a left side elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The structural features depicted by broken lines in the drawing views have been shown for the purpose of illustrating portions of the backpack that form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 